DESCRIPTION (Applicant's Abstract): Panic Disorder (PD) is a serious psychiatric illness which, if left untreated, can be associated with significant life dysfunction and distress. Although a number of controlled experimental studies have supported the efficacy of Panic Control Therapy (PCT) as a cognitive-behavioral treatment for PD, no studies have evaluated the transportability of PCT to real-world clinical practice. Investigating the outcomes of an empirically validated manual-based psychotherapy in clinical practice is a crucial step in disseminating effective treatments and working towards empirically-based standards of care. The purpose of this study is to investigate the impact of training in PCT for master's level therapists working in a managed care context. Ten clinicians will be randomly assigned to PCT training or treatment as usual (TAU). Patients meeting criteria for PD = 120) with varying degrees of severity and with or without agoraphobia will be randomly assigned to PCT-trained or TAU therapists. Outcomes will be evaluated at post-treatment, 3 months 1 year, and 2 years following treatment. Blind ratings of therapist adherence to PCT will provide an assessment of how well clinicians can learn and implement the protocol in clinical practice following state of the art training. By maintaining random assignment of therapists and patients, this study will possess the necessary internal validity to draw conclusions regarding the effectiveness of PCT in clinical practice. The use of non- expert master's level clinicians, and a more heterogeneous sample of patients than previous studies, will greatly enhance the generalizability of the findings, and speak to the effectiveness of PCT in real-world clinical practice.